However the reaction to the guilty verdict against Denis MacShane (followed by his six month jail conviction) yet again proves my point.

The Labour Party feels very little shame or anger at the behaviour of someone who embarked, quite deliberately, on a five-year-long criminal career when he was a minister of the crown. Instead it has directed its anger at the criminal justice system itself, which it believes has treated the Labour MP very unfairly.

Here is Tom Harris MP: "A number of us are very concerned now at this relentless destruction of a decent, hardworking MP's life." Mr Harris also said that "everyone in private agreed Denis was unjustly treated." For John Monks, former general secretary of the TUC, MacShane "was a cutter of corners, but not a venal crook."

Let’s look at the reporting from Patrick Wintour. The Guardian's political editor commented that MacShane’s "enemies will say he deserves his sentence … But his friends will defend him as a man who takes risks and places himself in danger."

Mr Wintour is plainly stating that those who support Mr MacShane’s jail sentence are the "enemies" of the former Labour MP. This is very troubling, because the Guardian political editor is implying that Mr Justice Sweeney, who imposed the sentence, is "an enemy" of Mr MacShane – and that his verdict can therefore be presumed to be biased.

Lord Brookman claimed in his MacShane’s defence that his trade union work was a "major factor" in the overthrow of Apartheid. The Left-wing political columnist Francis Beckett said that Mr MacShane was a "a man who took risk not in pursuit of financial gain but in pursuit of the public good". Chris Mullin, the former Labour MP, made the same claim: "Arguably, it was his passion for the EU that brought about his downfall."

There is a constant refrain in all the above arguments: the presumption on the Left that commitment to virtuous causes can be an excuse for criminal conduct.

The truth is that MacShane is a common criminal, as Mr Justice Sweeney pointed out when he delivered his judgment. This is what the judge said in his summing up:

In your case, you have no one to blame but yourself … there was deliberate, oft repeated and prolonged dishonesty over a period of years – involving a flagrant breach of trust and consequent damage to Parliament, with correspondingly reduced confidence in our priceless democratic system and the process by which it is implemented and we are governed.

The trouble is that neither MacShane nor the wider Labour Party seems able to come to terms with MacShane’s criminality. Consider MacShane’s contemptuous response when the judge sent him down: "Quelle surprise!" It must have come close to contempt of court because it undermined the authority of the judge and thus the rule of law. Young thugs have had their sentence doubled for less.

Or consider this comment from MacShane before Christmas. "What I did was worse than a crime, it was a stupid error."

This last remark displays an inability to distinguish between right and wrong. We all make stupid errors, and if we are sensible learn from them. But stupid errors are not morally wrong. Lying and cheating are morally wrong. Mr MacShane – and his many Labour Party supporters – badly need to learn the difference.

The origins of this confusion of ideas can partly be found in the student Marxism that infected so many Left-wing people at university. Karl Marx taught that morality – honesty, truth, the rule of law etc – were just "so many bourgeois prejudices".

But it primarily has its origins in the emergence of a political class which feels that it is entitled to rights, privileges, immunities and benefits which do not apply to ordinary people. Mr MacShane was an almost perfect embodiment of this political class. This is the main reason why fellow Labour MPs feel that he is a victim rather than a culprit, and that it is the British justice system rather than MacShane who has committed a crime.